Hm as i recall Ash Wheels & Tyres charged me £100 to fit my Eibach Pro Kit Springs...they have a website too they're based on the A12/Eastern Avenue off of Oaks Park Lane in East London/Ilford but this may be too far for you...also the price was decent because i'm a regular there and they know me lol but yeah anything between £100-£160'ish i'd say...you gotta take into account the 4 wheel alignment/cambers tracking you're gonna need to get done after letting the springs settle in for about 50-100 miles
Also seeing as you're going down the H&R route regardless of whether you were on SE or Msport before i dont know if you have but you better make sure you're changing your shock absorbers too...that's why i went for the Eibach Pro Kit because they're similar to the stock Msport so i didnt have to change anything apart from the springs but enough to close the gaps on the arches
Hope that helps!